This invention relates to systems for testing electronic circuits by applying and/or measuring electrical signals and, more particularly, to electronic circuit test systems for applying electrical signals to a packaged device or integrated circuit being tested and measuring the response of the device or integrated circuit to the applied electrical signals. Specifically, one embodiment of the invention provides a socket for effecting an electrical connection(s) in an electronic circuit tester between an electronic circuit, such as a packaged device or integrated circuit, being tested and a device-under-test (DUT) board that interfaces to a fixture board of the tester so that electrical signals can be transmitted to and/or received from the electronic circuit for characterizing the performance of the electronic circuit. The socket in accordance with one embodiment of the invention is particularly adaptable to a high-frequency electronic circuit tester for effecting connections between the electronic circuit being tested and the DUT board while minimizing parasitic inductance, capacitance, and phase delay of electrical signals, as well as for increasing repeatability of connections, to improve reliability and accuracy, thereby facilitating measurements with the tester for testing high-frequency devices and integrated circuits and enhancing overall throughput of the tester.
Programmable electronic circuit testers are typically used during the manufacture of electronic devices and integrated circuits to test the performance of the device or integrated circuit being manufactured. Tests are conducted to assure that the device or integrated circuit satisfies associated design performance specifications. In order to test the device or integrated circuit, the electronic circuit tester is programmed to inject an electrical signal or suite of electrical signals into the device or integrated circuit under test and to measure the response(s). For example, the electronic circuit tester can be used to test finished packaged devices and integrated circuits.
A conventional programmable electronic circuit tester, generally indicated by the numeral 10, is shown in FIG. 1. The electronic circuit tester 10 comprises a test head 12 electrically connected by cables routed through a conduit 14 to a rack(s) 16 of electronic test and measurement instruments, such as ac and dc electrical signal generators for applying electrical signals to a device or integrated circuit interfaced to the test head, and signal analyzers, for example, a network analyzer, spectrum analyzer, oscilloscope, or other waveform digitizing and/or signal processing equipment, for measuring the response(s) to those applied electrical signals. The test head 12 can include circuitry which performs distribution of electrical signals, signal separation, frequency translation, amplification, attenuation, switching, or other conditioning or modification of electrical signals prior to being routed to the rack 16 or to a device or integrated circuit being tested.
As shown in FIG. 1, the test head 12 interfaces to a device or integrated circuit through a load board 18 mounted to the test head and a fixture board 20 in turn mounted to the load board. Alternatively, prior to installation of the fixture board 20, a calibration board (not shown) having a configuration similar to the fixture board can be connected to the test head 12 for calibrating the test head. The configuration of the load board 18 depends on the type or family of device or integrated circuit being tested, such as an analog or digital electronic circuit, while the configuration of the fixture board 20 is typically specific to the family or particular device or integrated circuit being tested.
As shown in FIG. 1, the fixture board 20 is in turn interfaced to a DUT board 22 that comprises inductors, capacitors, and/or other electronic components or circuits mounted or fabricated on the DUT board for decoupling, filtering, attenuating, or otherwise modifying electrical signals transmitted to and/or received from a device or integrated circuit being tested. Finally, the DUT board 22 is connected to a socket 24 for effecting an electrical connection(s) between the electronic circuit tester 10 and the actual electric circuit being tested, such as a packaged device or integrated circuit 26.
As also shown in FIG. 1, the test head 12 is mounted on a dolly 28. The test head 12 is preferably mounted by pivotable connections 30 to the dolly 28. The pivotable connections 30 enable the test head 12 to be positioned in an approximately upward facing horizontal position so that the appropriate load board 18 and calibration or fixture board 20 and DUT board 22 with the socket 24 can be mounted on the test head of the electronic circuit tester 10 by an operator. The test head 12 can also be pivoted to any angular position so that the socket 24 can interface with a material handler (not shown), for example, to test the packaged device or integrated circuit 26.
The socket 24 through which the packaged device or integrated circuit 26 is electrically connected to the electronic circuit tester 10 is subjected to many connections and disconnections during actual testing with the tester. However, the useful life of the electronic circuit tester 10 has heretofore far exceeded the useful life of the socket 24. Also, the repeatability and accuracy of the connections that are effected by the socket 24 with the packaged device or integrated circuit 26 decreases over time as the socket degrades due to wear. Moreover, in an electronic circuit tester 10 for testing high-frequency devices and integrated circuits, the known configurations of the socket 24 have a significant electrical signal path length between the lead(s) of the packaged device or integrated circuit 26 being tested and the DUT board 22. This electrical signal path length adds inductance, as well as additional capacitance between leads of the packaged device or integrated circuit 26, which affects the accuracy of measurements and the operating characteristics and/or performance of the packaged device or integrated circuit being tested.
For example, one known socket 24 manufactured by Johnstech International Corporation located in Minneapolis, Minn., is shown in FIG. 2. See, also, U.S. Pat. Nos. 5,069,629 and 5,207,584. S-shaped contacts 32 introduce a significant electrical signal path length between contact with leads 34 of the packaged device or integrated circuit 26 being tested and the DUT board 22 at higher frequencies. The length of the S-shaped contacts 32 contributes added inductance, as well as additional capacitance between the leads 34 of the packaged device or integrated circuit 26. This results in parasitic inductance, capacitance, and phase delay in electrical signals applied to and/or the measured response(s) of the packaged device or integrated circuit 26, which affects the accuracy of the measurements and operating characteristics and/or performance of the packaged device or integrated circuit. The adverse effects increase as the frequency increases.
It would therefore be desirable to provide a socket structure to repeatably connect the packaged device or integrated circuit 26 to the DUT board 22 over a longer period of the useful life of the electronic circuit tester 10 during actual testing. Additionally, it is desirable to provide a relatively rugged socket structure which minimizes the parasitic inductance, capacitance, and electrical signal phase delay. Such a socket structure would improve the repeatability and accuracy of the electronic circuit tester 10 during actual testing.